Method For Control Of Linear Drive Devices For A Thread-Like Product In Particular A Textile Thread During The Start-Up Phase And Device For Carrying Out The Same

ABSTRACT

A control method for a motor driven linear drive device is provided in which: a device control unit receives information representative of measured speed of said device; on receiving a start-up command, start-up of the motor is not initiated if the measured speed is zero; information representative of the speed of the drive devices is monitored; and a control sequence which brings about rotation of the motor in accordance with a pre-programmed acceleration profile is initiated when rotation of the device caused by an external action is detected.

The invention relates to the technical field of installations or machinery for processing continuous elongated materials moved by transport along their own trajectory. Such continuous elongated materials include textile threads, ribbons, tapes, etc.

More especially, the invention relates to the control of means for transporting the material capable of feeding it along its own trajectory. Such means include, by way of information and merely by way of example, cylinders, pulleys, endless belts, rollers, godet rolls or other devices that transport the elongated material by friction, gripping, meshing etc.

Various technical solutions have been proposed for starting up machinery intended for processing elongated materials or other thread-like products. Based on the prior art, a distinction is essentially made between two solutions.

With the first solution (JP-A-52091912), the material is previously laid out along the transport route while the transport devices are switched off. This operation is referred to as “threading” in the case of machinery for processing textile threads. The transport devices are then switched on and gradually accelerated until they reach the required rated speed, depending on the work to be performed. Generally speaking, acceleration is programmed in accordance with synchronised ramp rates which maintain constant speed ratios. This solution makes it necessary to use synchronised means of starting and stopping. This solution cannot be used with certain devices such as those used in heat treatment which are likely to burn the material if it is static, given the fact that the material is not moving when start-up is initiated.

In contrast to this solution, another method involves starting the material transport devices in advance, running them up to their rated speed and then feeding in said material. The material is only fed into the input of the transport devices once the rated speed has been reached so that the material is snatched and instantly transported at rated speed. Generally speaking, the material is presented by a device that moves it at an initial speed that is close to the rated speed of the treatment process. For example, this device may consist of arms associated with suction nozzles such as those widely used on textile machinery.

This solution is nevertheless difficult to use in the case of high-speed processes involving fragile materials that cannot withstand the rapid acceleration encountered, generally speaking, when the material is snatched.

If this operation is performed manually, it requires great dexterity on the part of the operator.

It should also be noted that there are safety problems, given that operations are performed on moving parts.

Finally, there have been proposals to combine the two threading technical solutions explained above in some complex installations (U.S. Pat. No. 3,842,578). For example, threading is performed only on some of the switched-off devices, avoiding thermal devices, for instance, which cannot process material that is stationary. The installation is then started and run up to rated speed, transferring the moving material to the devices that were avoided during initial threading.

In this case too, the solution is relatively tricky to implement.

The invention has set itself the object of overcoming these drawbacks in a simple, dependable, effective and efficient manner.

The problem that the invention aims to solve is to control the devices used to transport thread-like products such as textile yarns, ribbons and tapes along their own trajectory during the start-up phase.

According to the invention, a method for control of linear drive devices for a thread-like product, in particular a textile thread, during the start-up phase has been devised, each of said devices being slaved to an electric motor, the motor being associated with at least one control unit capable of receiving speed and/or speed ratio set points and start/stop commands.

According to the invention, given the problem to be solved:

-   -   the device control unit is subjected to a means of measuring the         speed of said device;     -   on receiving a start-up command, start-up of the motor is not         initiated if the measured speed is zero;     -   information representative of the measured speed of the drive         device is monitored;     -   a control sequence which brings about rotation of the motor in         accordance with a pre-programmed acceleration profile is         initiated when rotation caused by an external action is         detected.

As a result of the basic characteristics of the invention, start-up mode can only be initiated if the motor is initially switched off. Changeover to this operating mode does not initiate the sequence to control the motor so as to cause immediate rotation of the latter in accordance with an acceleration profile. On the contrary, according to the invention, changeover to this operating mode may, if the technology of the motor so permits, cause creation of a limited torque to maintain switch-off. This torque may be parameterisable and monitored by voltage or current limiting for example.

The motor is kept switched off as long as rotation caused by an external action is not detected.

When rotation caused by an external action is detected, the control sequence which brings about rotation of the motor in accordance with a programmed acceleration profile is initiated.

In one preferred embodiment of the invention, when rotation caused by an external action is detected, information representative of the direction of rotation of the drive device is monitored and the control sequence which brings about rotation of the motor is initiated only if the direction of rotation matches a previously parameterised direction of rotation. If a non-matching direction of rotation is detected, the system may, if the technology of the motor so permits, cause creation of a resisting torque; this torque may be parameterisable and/or monitored by voltage or current limiting for example.

After receiving a start-up command, the process comprises:

-   -   a period during which the motor is kept switched off;     -   a period during which rotation is caused by an external action;     -   a period during which rotation is in accordance with the         acceleration profile;     -   a period of operation at rated speed.

According to the invention, the external action consists of driving the thread and/or the drive or transport device for said thread, said driving being obtained manually by an operator or by auxiliary means.

The acceleration profile is a linear ramp or a ramp of any shape whatsoever.

According to the invention, the acceleration profile may comprise a constant intermediate speed plateau that is different from the rated speed set point:

-   -   The intermediate speed of the plateau can be pre-programmed.     -   The intermediate speed of the plateau can be the rotation speed         created by the external action and measured briefly by the         control system after it is detected.     -   The duration of this plateau can be pre-programmed.     -   The speed plateau can be maintained until the control system         receives an acceleration command via an input/output or over the         network.

According to the invention, this control sequence determines (motor or brake) torque limiting monitored, for instance, by voltage or current limiting:

-   -   This torque limiting can be fixed.     -   This torque limiting can depend on the rotation speed.     -   This torque limiting can be maintained for a pre-programmed         time.     -   This torque limiting can be maintained until the speed reaches         the speed of the intermediate speed plateau.     -   This torque limiting can be maintained until the end of the         intermediate speed plateau.     -   This torque limiting can be maintained until the speed reaches         the rated speed set point.

In order to use the method according to the invention, the device comprises thread transport devices slaved to at least one control unit capable of receiving at least one speed signal, the motor being a variable-reluctance or permanent-magnet motor, the power supply sequence of which is a sequence for switching the power supplies of its windings synchronised by signals representative of the position of the rotor relative to the stator, said signals being capable of being used in order to measure and detect the rotation speed.

The motor may be also be an induction or other type of motor.

According to the invention, the device to transport a thread-like material may comprise several components that act together in combination.

In this case, each transport device has an individual start-up tracking mode, sensors that output signals representative of its speed and means of waiting for rotation caused by an external action in order to accelerate in accordance with its own acceleration profile.

Alternatively, only one of the transport devices has an individual start-up tracking mode and the control system is programmed to keep the speed ratios of the other device(s) constant relative to said device that has the tracking mode, which is a means of measuring its rotation speed, the speed ratio(s) being predetermined by parameter adjustment.

Detection of the speed caused by an external action, management of acceleration profiles and, more generally, execution of the tracking sequence are performed by a program executed by a central processing unit and/or the processor.

The invention is explained below in greater detail, reference being made to the accompanying drawings in which:

FIG. 1 shows an example of an embodiment of the method for control of transport of a thread-like product associated with a control unit;

FIG. 2 is a curve showing an example of an acceleration profile;

FIG. 3 is a curve showing an example of an acceleration profile with a pre-programmed speed plateau;

FIG. 4 is a curve showing an example of an acceleration profile with a speed plateau equal to the speed resulting from an external action.

In each of FIGS. 2, 3 and 4:

-   -   (A) is the period during which the device waits to be rotated:     -   (B) shows the period during which rotation is caused by an         external action (if applicable, broken down into detection         period (B1) and speed measurement (B2));     -   (C) is equivalent to the period during which rotation is in         accordance with the acceleration profile (if applicable, broken         down into acceleration phase and speed plateaux (C1), (C2),         (C3), etc.);     -   (D) is equivalent to the period of operation at rated speed.

FIG. 1 shows an example of a transport device (1) in the form, for example, of a godet roll capable of driving a thread-like product such as, for instance, a textile thread. Device (1) is driven by electric motor (2) slaved to a control unit (3) that is connected to an electric power supply (4). Control unit (3) comprises, for example, a power supply (5), power circuitry (7) and a processor (6) slaved to a central processing unit (9) in the form of, for instance, a PC, automaton or printed circuit board, etc. Means (8) are capable of delivering a signal representative of the rotation speed of transport devices (1).

According to the invention, processor (6) receives speed or speed ratio set points from central processing unit (9) over network (10) as well as the operating parameters of transport devices (1) controlled by motors (2). If applicable, processor (6) may receive start, stop, etc. commands via the network or via other inputs/outputs.

The control unit (3) of electric motors (2) receives information representative of the speed of means (1) that transports the thread-like product.

According to one basic aspect of the invention, at least one of the transport devices is subjected to a particular start-up mode characterised by the following essential arrangements:

-   -   this start-up mode is initiated when the motor is initially         switched off;     -   changeover to the operating mode does not initiate a sequence to         control the motor so as to cause immediate rotation of the         latter in accordance with an acceleration profile and may, if         applicable and if the technology of the motor so permits, cause         creation of a limited torque to maintain switch-off;     -   the control unit monitors the information representative of the         speed (phase (A)) of the transport devices so that switch-off         (and if applicable, the limited torque to maintain switch-off)         is maintained as long as rotation resulting from an external         action is not detected.

This external action may consist of driving the thread and/or device (1) (phase B), it being possible to obtain said driving manually by the operator or by any auxiliary means.

When external action is detected, control unit (3) initiates a sequence to control motor (2) (phase (C)) in accordance with a pre-programmed acceleration profile.

According to one enhancement of the invention, information representative of the direction of rotation of drive device (1) is available, for example, in association with information representative of the speed of said drive device. When rotation caused by an external action is detected, control unit (3) checks the direction of this rotation and only initiates the control sequence which brings about rotation of motor (2) if the direction of rotation matches a parameterised direction of rotation.

If a non-matching direction of rotation is detected, control unit (3) may, if the technology of the motor so permits, cause creation of a resisting torque; this torque may be parameterisable and/or monitored by voltage or current limiting for example.

In FIGS. 2, 3 and 4 which show various examples of speed curves, (A) is the period during which the motor is kept switched off, (B) is the period during which rotation is caused by an external action, (C) is the period during which rotation is in accordance with the acceleration profile and (D) is the period of operation at rated speed.

In these curves, (11) represents a rated set-point speed and (12) represents acceleration along a linear ramp (FIGS. 2 and 4) or several ramps (12 a), (12 b) (FIG. 3). As shown in FIGS. 3 and 4, the acceleration profile may include a plateau (13, 14) at a constant intermediate speed that is different from the rated set-point speed (11). The intermediate speed of the plateau can pre-programmed or be the rotation speed created by the external action and measured briefly by the control system after it is detected. The duration of the speed plateau can be pre-programmed and its speed can be maintained until the control unit receives an acceleration command.

Note that, when the control sequence determines a torque monitored, for example, by voltage or current limiting, the torque can be fixed or can depend on the rotation speed and be maintained for a pre-programmed time or until the speed reaches the plateau speed and the intermediate speed or it can be maintained until the end of the intermediate speed plateau or be maintained until the speed reaches the rated-speed set point.

If motor (2) is a variable-reluctance or permanent-magnet motor, the power supply sequence is a sequence for switching the power supplies of the windings synchronised by signals representative of the position of the rotor relative to the stator (Hall-effect sensors) or sensors for measuring the current in the windings that are representative of the position of the rotor relative to the stator. The signals obtained from these sensors can be used by processor (6) in order to detect and measure the rotation speed.

The signals obtained from these sensors can also be used to determine the direction of rotation of the motor.

According to the invention, the device to drive the thread-like material may comprise several transport components, each driven by a motor (2).

In this case, either each transport device (1) has an individual start-up tracking mode or only one of the transport devices (1) has an individual start-up tracking mode.

If each transport device has an individual start-up tracking mode, each of the devices has sensors outputting signals representative of these speeds. Each device will wait to be rotated by an external action in order to accelerate according to its own acceleration profile.

If only one of the transport devices has an individual start-up and tracking mode, the control system is pre-programmed to keep the speed ratios of the motor(s) that does/do not have an individual start-up tracking mode constant relative to the motor that does have such a mode.

The motor equipped with an individual start-up tracking mode is fitted with sensors or means of measuring its rotation speed with the speed ratio(s) being predetermined by parameter adjustment. In this way it is possible to control all the motors by controlling the speed of the motor(s) that does/do not have an individual start-up tracking mode in synchronism or by tracking the speed of the motor that does have such a mode.

Note that the device uses a program capable of ensuring detection of the speed caused by an external action, management of acceleration profiles and, generally speaking, execution of the tracking sequence as described. Note that these various functions can be performed by a program executed by processor (6) of control unit(s) (3) or by a combination of central processing unit (9) and processor (6) (FIG. 1).

The advantages of the invention are readily apparent from the description, the following features in particular being emphasised and underlined:

-   -   the operator can initiate transport by making a single movement         completely safely by causing rotation when required,     -   start-up can be gradual without any sudden transition at the         instant the thread is applied to the drive device. 

1. A method for control of linear drive devices for a thread-like product, in particular a textile thread, during a start-up phase, each of said devices being slaved to an electric motor, the motor being associated with at least one control unit capable of receiving speed and/or speed ratio set points and start/stop commands, wherein: the device control unit is subjected to a means of measuring the speed of said device; on receiving a start-up command, start-up of the motor is not initiated if measured speed of the device is zero; information representative of the speed of at least one of the drive devices is monitored; and a control sequence which brings about rotation of the motor in accordance with a pre-programmed acceleration profile is initiated when rotation of the device caused by an external action is detected.
 2. A method as claimed in claim 1, wherein, when rotation of drive device caused by an external action is detected, a control sequence which brings about rotation of the motor is only initiated if a direction of said rotation matches a pre-determined direction of rotation.
 3. A method as claimed in claim 2, wherein, if the direction of the detected rotation caused by an external action is opposite to a parameterized direction of rotation, resisting torque is created.
 4. A method as claimed in claim 1, wherein when the start-up command is received, a limited torque to maintain switch-off is created.
 5. A method as claimed in claim 1, wherein the external action comprises driving the thread and/or the drive device, said driving being obtained manually by an operator or by auxiliary means.
 6. A method as claimed in claim 1, wherein a start-up process of the device comprises: a period during which the motor is kept switched off; a period during which rotation is caused by an external action; a period during which rotation is in accordance with the pre-programmed acceleration profile; and a period of operation at rated speed.
 7. A method as claimed in claim 1, wherein the pre-programmed acceleration profile comprises a linear ramp or ramp of any shape whatsoever.
 8. A method as claimed in claim 1, wherein: the pre-programmed acceleration profile comprises a plateau of constant intermediate speed that is different from a rated speed set point; and said intermediate speed is pre-programmed or a rotation speed created by the external action and measured briefly by the means after the external action is detected.
 9. A method as claimed in claim 8, wherein: a duration of the plateau is pre-programmed; and the speed plateau is maintained until the control unit receives an end-of “tracking” mode command or command to change to normal operating mode via an input/output or over a network.
 10. A method as claimed in claim 3, wherein the torque is limited during execution of an acceleration phase.
 11. A method as claimed in claim 10, wherein the limiting of the torque is fixed and depends on the rotation speed.
 12. A method as claimed in claim 10, wherein torque limiting is maintained for a pre-programmed time until the speed reaches a speed of an intermediate speed plateau; or until an end of the intermediate speed plateau; or until the speed reaches a rated speed set point; or until the control unit receives an end-of “tracking” mode command or command to change to normal operating mode via an input/output or over a network.
 13. Apparatus for using the method according to claim 1, comprising several thread drive devices, at lease one thread drive device being slaved to a motor associated with a control unit capable of receiving a speed signal, wherein the motor is a variable-reluctance or permanent-magnet motor, a power supply sequence of the motor comprises a sequence for switching power supplies of motor windings synchronized by signals representative of position of a rotor relative to a stator of the motor, said signals being sent to a processor in order to measure and detect the rotation speed of the at least one thread drive device.
 14. Apparatus as claimed in claim 13, wherein the signals representative of the position of the rotor relative to the stator are used by the processor in order to determine direction of rotation of the at least one device.
 15. Apparatus for using the method as claimed in claim 12, wherein the several drive devices cooperate with each other in order to drive a single thread.
 16. Apparatus as claimed in claim 15, wherein each drive device has an individual start-up tracking mode, sensors that output signals representative of device rotation speed and means of waiting for rotation caused by an external action in order to accelerate in accordance with a respective acceleration profile.
 17. Apparatus as claimed in claim 15, wherein only one device of the drive devices has an individual start-up tracking mode, and further comprising a control system programmed to keep speed ratios of other devices constant relative to said one device that has the tracking mode, means of measuring rotation speed of the one device, and the speed ratios being predetermined by parameter adjustment.
 18. A device as claimed in claim 17, wherein detection of the speed caused by an external action, management of acceleration profiles and, execution of the tracking sequence are performed by a program executed by a central processing unit and/or the control unit.
 19. The method of claim 3, wherein the resisting torque is parameterized and/or monitored by voltage or current limiting. 